Typical compartment bulkheads used on aircraft are designed utilizing non-metallic composite hybrid thermosetting phenolic resin sandwich panels that can be peripherally framed or not, depending on the space and design requirements unique to each bulkhead location. Framed panels are used in areas where aircraft structures do not allow sufficient edge margin space typically required for non-framed monolithic composite panels. Framed panels are also used in areas where extreme heat resistance and low smoke vapor toxicity emissions are required, or where the panel will be frequently removed in service, such as a maintenance access cover, and where fastener hole wear resistance is required. Framed panels are used to prevent face sheets from delaminating from the composite panel core resulting from in service abuse.
Exemplary of prior art panel structures utilized in aircraft is U.S. Pat. No. 4,557,961 to Gorges issued Dec. 10, 1985 and assigned to The Boeing Company.
The state of the art metal-framed panel designs are labor intensively built from multiple details which include machined parts, stretch formed parts, profiled extrusions, blanked sheet metal parts, non-metallic subassemblies and associated standards. Fabrication of the panel assemblies usually requires large tools to hold the panel periphery while the assembly of the panels is completed so that the edge margin alignment is maintained. Splice plates or integrated overlaps are required to attach one segment of the frame to another and all of these frame splices are completed using fasteners. Existing designs usually require a post assembly drilling operation utilizing drill templates or numerical control programs in efforts to provide controlled fastener patterns. Once the frames have been assembled, additional labor intensive operations are required to seal and finish the panel, i.e., masking, local trimming, local primer touch up, enamel application and silicon sealing.